1. Field of the Invention
This invention relates to compounds which inhibit xcex2-amyloid peptide release and/or its synthesis, and, accordingly, have utility in treating Alzheimer""s disease. This invention also relates to pharmaceutical compositions comprising such compounds as well as methods for inhibiting release of xcex2-amyloid peptide.
2. References
The following publications, patents and patent applications are cited in this application as superscript numbers:
1 Glenner, et al., xe2x80x9cAlzheimer""s Disease: Initial Report of the Purification and Characterization of a Novel Cerebrovascular Amyloid Proteinxe2x80x9d, Biochem. Biophys. Res. Commun., 120:885-890 (1984).
2 Glenner, et al., xe2x80x9cPolypeptide Marker for Alzheimer""s Disease and its Use for Diagnosisxe2x80x9d, U.S. Pat. No. 4,666,829 issued May 19, 1987.
3 Selkoe, xe2x80x9cThe Molecular Pathology of Alzheimer""s Diseasexe2x80x9d, Neuron, 6:487-498 (1991).
4 Goate, et al., xe2x80x9cSegregation of a Missense Mutation in the Amyloid Precursor Protein Gene with Familial Alzheimer""s Diseasexe2x80x9d, Nature, 349:704-706 (1990).
5 Chartier-Harlan, et al. xe2x80x9cEarly-Onset Alzheimer""s Disease Caused by Mutations at Codon 717 of the xcex2-Amyloid Precursor Protein Genexe2x80x9d, Nature, 353:844-846 (1989).
6 Murrell, et al., xe2x80x9cA Mutation in the Amyloid Precursor Protein Associated with Hereditary Alzheimer""s Diseasexe2x80x9d, Science, 254:97-99 (1991).
7 Mullan, et al., xe2x80x9cA Pathogenic Mutation for Probable Alzheimer""s Disease in the APP Gene at the N-Terminus of xcex2-Amyloid, Nature Genet., 1:345-347 (1992).
8 Schenk, et al., xe2x80x9cMethods and Compositions for the Detection of Soluble xcex2-Amyloid Peptidexe2x80x9d, International Patent Application Publication No. WO 94/10569, published May 11, 1994.
9 Selkoe, xe2x80x9cAmyloid Protein and Alzheimer""s Diseasexe2x80x9d, Scientfic American, pp. 2-8, November, 1991.
10 Yates, et al., xe2x80x9cN,N-Disubstituted Amino Acid Herbicidesxe2x80x9d, U.S. Pat. No. 3,598,859, issued Aug. 10, 1971.
11 Citron, et al., xe2x80x9cMutation of the xcex2-Amyloid Precursor Protein in Familial Alzheimer""s Disease Increases xcex2-Protein Production, Nature, 360:672-674 (1992).
12 Hansen, et al., xe2x80x9cReexamination and Further Development of a Precise and Rapid Dye Method for Measuring Cell Growth/Cell Killxe2x80x9d, J. Immun. Meth., 119:203-210 (1989).
All of the above publications, patents and patent applications are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety.
State of the Art
Alzheimer""s Disease (AD) is a degenerative brain disorder characterized clinically by progressive loss of memory, cognition, reasoning, judgment and emotional stability that gradually leads to profound mental deterioration and ultimately death. AD is a very common cause of progressive mental failure (dementia) in aged humans and is believed to represent the fourth most common irredical cause of death in the United States. AD has been observed in races and ethnic groups worldwide and presents a major present and future public health problem. The disease is currently estimated to affect about two to three million individuals in the United States alone. AD is at present incurable. No treatment that effectively prevents AD or reverses its symptoms and course is currently known.
The brains of individuals with AD exhibit characteristic lesions termed senile (or amyloid) plaques, amyloid angiopathy (amyloid deposits in blood vessels) and neurofibrillary tangles. Large numbers of these lesions, particularly amyloid plaques and neurofibrillary tangles, are generally found in several areas of the human brain important for memory and cognitive function in patients with AD. Smaller numbers of these lesions in a more restrictive anatomical distribution are also found in the brains of most aged humans who do not have clinical AD. Amyloid plaques and amyloid angiopathy also characterize the brains of individuals with Trisomy 21 (Down""s Syndrome) and Hereditary Cerebral Hemorrhage with Amyloidosis of the Dutch Type (HCHWA-D). At present, a definitive diagnosis of AD usually requires observing the aforementioned lesions in the brain tissue of patients who have died with the disease or, rarely, in small biopsied samples of brain tissue taken during an invasive neurosurgical procedure.
The principal chemical constituent of the amyloid plaques and vascular amyloid deposits (amyloid angiopathy) characteristic of AD and the other disorders mentioned above is an approximately 4.2 kilodalton (kD) protein of about 39-43 amino acids designated the xcex2-amyloid peptide (xcex2AP) or sometimes Axcex2, Axcex2P or xcex2/A4. xcex2-Amyloid peptide was first purified and a partial amino acid sequence was provided by Glenner, et al.1 The isolation procedure and the sequence data for the first 28 amino acids are described in U.S. Pat. No. 4,666,8292.
Molecular biological and protein chemical analyses have shown that the xcex2-amyloid peptide is a small fragment of a much larger precursor protein (APP), that is normally produced by cells in many tissues of various animals, including humans. Knowledge of the structure of the gene encoding the APP has demonstrated that xcex2-amyloid peptide arises as a peptide fragment that is cleaved from APP by protease enzyrne(s). The precise biochemical mechanism by which the xcex2-amyloid peptide fragment is cleaved from APP and subsequently deposited as amyloid plaques in the cerebral tissue and in the walls of the cerebral and meningeal blood vessels is currently unknown.
Several lines of evidence indicate that progressive cerebral deposition of xcex2-amyloid peptide plays a seminal role in the pathogenesis of AD and can precede cognitive symptoms by years or decades. See, for example, Selkoe3. The most important line of evidence is the discovery that missense DNA mutations at amino acid 717 of the 770-amino acid isoform of APP can be found in affected members but not unaffected members of several families with a genetically determined (familial) form of AD (Goate, et al.4; Chartier Harlan, et al.5; and Murrell, et al.6) and is referred to as the Swedish variant. A double mutation changing lysine595-methionine596 to asparagine595-leucine596 (with reference to the 695 isoform) found in a Swedish family was reported in 1992 (Mullan, et al.7). Genetic linkage analyses have demonstrated that these mutations, as well as certain other mutations in the APP gene, are the specific molecular cause of AD in the affected members of such families. In addition, a mutation at amino acid 693 of the 770-amino acid isoform of APP has been identified as the cause of the xcex2-amyloid peptide deposition disease, HCHWA-D, and a change from alanine to glycine at amino acid 692 appears to cause a phenotype that resembles AD is some patients but HCHWA-D in others. The discovery of these and other mutations in APP in genetically based cases of AD prove that alteration of APP and subsequent deposition of its xcex2-amyloid peptide fragment can cause AD.
Despite the progress which has been made in understanding the underlying mechanisms of AD and other xcex2-amyloid peptide related diseases, there remains a need to develop methods and compositions for treatment of the disease(s). Ideally, the treatment methods would advantageously be based on drugs which are capable of inhibiting xcex2-amyloid peptide release and/or its synthesis.
This invention is directed to the discovery of a class of compounds which inhibit xcex2-amyloid peptide release and/or its synthesis and, therefore, are useful in the prevention of AD in patients susceptible to AD and/or in the treatment of patients with AD in order to inhibit further deterioration in their condition. The class of compounds having the described properties are defined by formula I below: 
wherein:
R1 is selected from the group consisting of
(a) phenyl,
(b) a substituted phenyl group of formula II: 
xe2x80x83wherein Rc is selected from the group consisting of acyl, alkyl, alkoxy, alkylalkoxy, azido, cyano, halo, hydrogen, nitro, trihalomethyl, thioalkoxy, and wherein Rb and Rc are fused to form a heteroaryl or heterocyclic ring with the phenyl ring,
Rb and Rbxe2x80x2 are independently selected from the group consisting of hydrogen, halo, nitro, cyano, trihalornethyl, alkoxy, and thioalkoxy with the proviso that when Rc is hydrogen, then Rb and Rbxe2x80x2 are either both hydrogen or both substituents other than hydrogen,
(c) 2-naphthyl,
(d) 2-naphthyl substituted at the 4, 5, 6, 7 and/or 8 positions with 1 to 5 substituents selected from the group consisting of alkyl, alkoxy, halo, cyano, nitro, trihalomethyl, thioalkoxy, aryl, and heteroaryl,
(e) heteroaryl, and
(f) substituted heteroaryl containing 1 to 3 substituents selected from the group consisting of alkyl, alkoxy, aryl, aryloxy, cyano, halo, nitro, heteroaryl, thioalkoxy and thioaryloxy provided that said substituents are not ortho (adjacent) to the heteroaryl attachment to the xe2x80x94NH group;
R2 is selected from the group consisting of hydrogen, alkyl of from 1 to 4 carbon atoms, alkylalkoxy of from 1 to 4 carbon atoms, alkylthioalkoxy of from 1 to 4 carbon atoms, aryl, heteroaryl, substituted aryl and substituted heteroaryl provided that the substituents are not ortho (adjacent) to the attachment of the aryl or heteroaryl atom to the carbon atom;
R3 is selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, cycloalkyl, cycloalkenyl, heteroaryl, substituted alkyl, substituted alkenyl, substituted alkynyl, and heterocyclic;
X is xe2x80x94C(O)Y where Y is selected from the group consisting of
(a) alkyl,
(b) substituted alkyl with the proviso that the substitution on said substituted alkyl does not include xcex1-haloalkyl, xcex1-diazoalkyl or xcex1-OC(O)alkyl groups,
(c) alkoxy or thioalkoxy,
(d) substituted alkoxy or substituted thioalkoxy,
(e) hydroxy,
(f) aryl,
(g) heteroaryl,
(h) heterocyclic,
(i) xe2x80x94NRxe2x80x2Rxe2x80x3 where Rxe2x80x2 and Rxe2x80x3 are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl, heterocyclic, and where Rxe2x80x2 and Rxe2x80x3 are joined to form a cyclic group having from 2 to 8 carbon atoms optionally containing 1 to 2 additional heteroatoms selected from the group consisting of oxygen, sulfur and nitrogen and optionally substituted with one or more alkyl or alkoxy groups, and
when R3 contains at least 3 carbon atoms, X can also be xe2x80x94CR4R4Yxe2x80x2 where each R4 is independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic and Yxe2x80x2 is selected from the group consisting of hydroxyl, amino, thiol, xe2x80x94OC(O)R5, xe2x80x94SSR5, xe2x80x94SSC(O)R5 where R5 is selected from the group consisting of alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic,
and with the proviso that when R1 is 3,4-dichlorophenyl, R2 is methyl, and R3 is benzyl derived from D-phenylalanine, then X is not xe2x80x94C(O)OCH3.
Accordingly, in one of its method aspects, this invention is directed to a method for inhibiting xcex2-amyloid peptide release and/or its synthesis in a cell which method comprises administering to such a cell an amount of a compound or a mixture of compounds of formula I above effective in inhibiting the cellular release and/or synthesis of xcex2-anmyloid peptide.
Because the in vivo generation of xcex2-amyloid peptide is associated with the pathogenesis of AD8,9, the compounds of formula I can also be employed in conjunction with a pharmaceutical composition to prophylactically and/or therapeutically prevent and/or treat AD. Accordingly, in another of its method aspects, this invention is directed to a prophylactic method for preventing the onset of AD in a patient at risk for developing AD which method comprises administering to said patient a pharmaceutical composition comprising a pharmaceutically inert carrier and an effective amount of a compound or a mixture of compounds of formula I above.
In yet another of its method aspects, this invention is directed to a therapeutic method for treating a patient with AD in order to inhibit further deterioration in the condition of that patient which method comprises administering to said patient a pharmaceutical composition comprising a pharmaceutically inert carrier and an effective amount of a compound or a mixture of compounds of formula I above.
In formula I above, R1 substituted phenyls are preferably 4-substituted, 3,5-disubstituted or 3,4-disubstituted phenyl substituents wherein the substituents at the 3 and/or 5 positions are defined by Rb, Rbxe2x80x2 as above and the substituents at the 4 position is defined by Rc as above. Particularly preferred 3,5-disubstituted phenyls include, by way of example, 3,5-dichlorophenyl, 3,5-difluorophenyl, 3,5-di(trifluoromethyl)phenyl, 3,5-dimethoxyphenyl, and the like. Particularly, preferred 3,4-disubstituted phenyls include, by way of example, 3,4-dichlorophenyl, 3,4-difluorophenyl, 3-(trifluoromethyl)-4-chlorophenyl, 3-chloro-4-cyanophenyl, 3-chloro-4-iodophenyl, 3,4-methylenedioxyphenyl, and the like. Particularly preferred 4-substituted phenyls include, by way of example, 4-azidophenyl, 4-bromophenyl, 4-chlorophenyl, 4cyanophenyl, 4-ethylphenyl, 4-fluorophenyl, 4-iodophenyl, 4-(phenylcarbonyl)phenyl, 4-(1-ethoxy)ethylphenyl, and the like.
Other preferred R1 substituents include, by way of example, 2-naphthyl, quinolin-3-yl, 2-methylquinolin-6-yl, benzothiazol-6-yl, benzothiazol-2-yl, 5-indolyl, phenyl, 2-naphthyl, and the like.
Preferably R2 is selected from the group consisting of alkyl of from 1 to 4 carbon atoms, alkylalkoxy of from 1 to 4 carbon atoms, alkylthioalkoxy of from 1 to 4 carbon atoms, aryl, heteroaryl, substituted aryl and substituted heteroaryl provided that the substituents are not ortho to the attachment of the aryl or heteroaryl atom to the carbon atom. Particularly preferred R2 substituents include, by way of example, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, xe2x80x94CH2CH2SCH3, phenyl and the like.
Preferred R3 substituents include alkyl groups such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-bulyl, sec-butyl, and the like; substituted alkyl groups such as xcex1-hydroxyethyl, xe2x80x94CH2-cyclohexyl, benzyl, p-hydroxybenzyl, 3-iodo-4-hydroxybenzyl, 3,5-diiodo-4-hydroxybenzyl, xe2x80x94CH2-indol-3-yl, phenyl, xe2x80x94(CH2)4xe2x80x94NH-BOC, xe2x80x94(CH2)4xe2x80x94NH2, xe2x80x94CH2xe2x80x94(1-N-benzyl-imidazol-4-yl), xe2x80x94CH2xe2x80x94imidazol-4-yl, xe2x80x94CH2CH2SCH3, xe2x80x94(CH2)4NHC(O)(CH2)4CH3, xe2x80x94(CH2)yC(O)OR5 where y is 1 or 2 and R5 is hydrogen, methyl, tert-butyl, phenyl, and the like.
Preferred X substituents include xe2x80x94C(O)Y groups where Y is methoxy, ethyoxy, n-propoxy, iso-propoxy, n-butoxy, iso-butoxy, tert-butoxy, amino (xe2x80x94NH2), N-(iso-butyl)amino, N-methylamino, N,N-dimethylamino, N-benzylamino, and the like as well as where X is xe2x80x94CH2OH and the like.
This invention also provides for novel pharmaceutical compositions comprising a pharmaceutically inert carrier and a compound of the formula I above.
Particularly preferred compounds for use in the methods and compositions of this invention include, by way of example, the following wherein the stereochemistry of the R2 and R3 groups is preferably derived from the L-amino acid:
N-[N-(3,4-dichlorophenyl)alanyl]valine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]valine N-iso-butyl amide
N-[N-(3,4-dichlorophenyl)alanyl]threonine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]valine ethyl ester
N-[N-(3,4-dichlorophenyl)alanyl]valine tert-butyl ester
N-[N-(3,4-dichlorophenyl)alanyl]valine amide
N-(3,4-dichlorophenyl)alanine N-(1-hydroxy-3-methyl-2-butyl) amide
N-[N-(3,4-dichlorophenyl)alanyl]valine N,N-dimethyl amide
N-[N-(3,4-dichlorophenyl)alanyl]valine N-methyl amide
N-[N-(3,4-dichlorophenyl)alanyl]alanine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]leucine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]phenylalanine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]isoleucine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]-2-aminopentanoic acid methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]-2-aminohexanoic acid methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]tryptophan methyl ester
N-[N-(3,4-dichlorophenyl)alinyl]aspartic acid xcex1-methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]aspartic acid xcex2-(tert-butyl ester) xcex1-methyl ester
N-[N-(3,4-dichlorophenyl)alinyl]-N-BOC-lysine methyl ester
N-[N-benzothiazol-6-yl)aianyl]-2-aminohexanoic acid methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]lysine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]tyrosine methyl ester
N-[N-(3,5-dichlorophenyl)alanyl]alanine methyl ester
N-[N-(3,5-dichlorophenyl)alanyl]-2-aminopentanoic acid methyl ester
N-[N-(3,5-dichlorophenyl)alanyl]phenylalanine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]aspartic acid xcex2-(methyl ester) xcex1-methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]-1-benzylhistidine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]glutamic acid xcex3-(tert-butyl ester) xcex1-methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]leucine amide
N-[N-(3,4-dichlorophenyl)alanyl]glutamic acid xcex1-methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]-(3,5-diiodo)tyrosine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]-(3-iodo)tyrosine methyl ester
N-[N-(3,5-dichlorophenyl)glycyl]-2-aminopentanoic acid methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]-Nxcex5-(hexanoyl)lysine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]phenylalanine amide
N-[N-(3,4-dichlorophenyl)alanyl]-2-aminohexan-(N-methyl)-amide
N-[N-(3,4-dichlorophenyl)alanyl]-xcex2cyclohexylalanine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]-2-aminohexanamide
N-[N-(3,4-dichlorophenyl)alanyl]-2-aminohexan-(N,N-dimethyl)-amide
N-[N-(3,4-dichlorophenyl)alanyl]methionine methyl ester
N-[N-(3,5-dichlorophenyl)alanyl]-2-aminohexan-(N,N-dimethyl)-amide
N-[N-(3,5-dichlorophenyl)alanyl]-2-aminohexanamide
N-[N-(3,5-dichlorophenyl)alanyl]-2-aminohexan-(N-methyl)-amide
N-[N-(3,4-dichlorophenyl)alanyl]histidine methyl ester
N-[N-(quinolin-3-yl)alanyl]-2-aminohexanoic acid methyl ester
N-[N-(benzothiazol-2-yl)alanyl]2-aminohexanoic acid methyl ester
N-[N-(3,5-difluorophenyl)alanyl]alanine methyl ester
N-[N-(3,5-difluorophenyl)alanyl]-2-aminohexanoic acid methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]-2-aminohexanamide
N-[N-(3,4-dichlorophenyl)alanyl]-2-aminohexan-(N-benzyl)-amide
N-[N-(3,4-dichlorophenyl)alanyl]-2-amino-2-phenylethanol
N-[N-(3,5-dichlorophenyl)phenylglycinyl]alanine methyl ester
N-[N-(3,4-dichlorophenyl)alanyl]-2-aminohexanol
N-[N-(3,5-dichlorophenyl)alanyl]-2-amino-2-phenylethanol
N-[N-(3,5-dichlorophenyl)alanyl]-phenylglycine tert-butyl ester
N-[N-(3,5-di-(trifluoromethyl)phenyl)alanyl]-phenylglycine tert-butyl ester
N-[N-(3,5-dimethoxyphenyl)alanyl]-2-aminohexanoic acid methyl ester
and pharmaceutically acceptable salts thereof.
Still further, this invention provides for novel compounds of the formula III: 
wherein:
R1 is selected from the group consisting of
(a) phenyl,
(b) a substituted phenyl group of formula II: 
xe2x80x83wherein Rc is selected from the group consisting of acyl, alkyl, alkoxy, alkylalkoxy, azido, cyano, halo, hydrogen, nitro, trihalomethyl, thioalkoxy, and wherein Rb and Rc are fused to form a heteroaryl or heterocyclic ring with the phenyl ring,
Rb and Rbxe2x80x2 are independently selected from the group consisting of hydrogen, halo, nitro, cyano, trihalomethyl, alkoxy, and thioalkoxy with the proviso that when Rc is hydrogen, then Rb and Rbxe2x80x2 are either both hydrogen or both substituents other than hydrogen,
(c) 2-naphthyl,
(d) 2-naphthyl substituted at the 4, 5, 6, 7 and/or 8 positions with 1 to 5 substituents selected from the group consisting of alkyl, alkoxy, halo, cyano, nitro, trihalomethyl, thioalkoxy, aryl, and heteroaryl,
(e) heteroaryl, and
(f) substituted heteroaryl containing 1 to 3 substituents selected from the group consisting of alkyl, alkoxy, aryl, aryloxy, cyano, halo, nitro, heteroaryl, thioalkoxy and thioaryloxy provided that said substituents are not ortho to the heteroaryl attachment to the xe2x80x94NH group;
R2 is selected from the group consisting of hydrogen, alkyl of from 1 to 4 carbon atoms, alkylalkoxy of from 1 to 4 carbon atoms, alkylthioalkoxy of from 1 to 4 carbon atoms, aryl, heteroaryl, substituted aryl and substituted heteroaryl provided that the substituents are not ortho to the attachment of the aryl or heteroaryl atom to the carbon atom;
R3 is selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, cycloalkyl, cycloalkenyl, heteroaryl, substituted alkyl, substituted alkenyl, substituted alkynyl, and heterocyclic;
X is xe2x80x94C(O)Y where Y is selected from the group consisting of
(a) alkyl,
(b) substituted alkyl with the proviso that the substitution on said substituted alkyl does not include xcex1-haloalkyl, xcex1-diazoalkyl or xcex1-OC(O)alkyl groups,
(c) alkoxy or thioalkoxy,
(d) substituted alkoxy or substituted thioalkoxy,
(e) hydroxy,
(f) aryl,
(g) heteroaryl,
(h) heterocyclic,
(i) xe2x80x94NRxe2x80x2Rxe2x80x3 where Rxe2x80x2 and Rxe2x80x3 are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl, heterocyclic, and where Rxe2x80x2 and Rxe2x80x3 are joined to form a cyclic group having from 2 to 8 carbon atoms optionally containing 1 to 2 additional heteroatoms selected from the group consisting of oxygen, sulfur and nitrogen and optionally substituted with one or more alkyl or alkoxy groups, and
when R3 contains at least 3 carbon atoms, X can also be xe2x80x94CR4R4Yxe2x80x2 where each R4 is independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic and Yxe2x80x2 is selected from the group consisting of hydroxyl, amino, thiol, xe2x80x94OC(O)R5, xe2x80x94SSR5, xe2x80x94SSC(O)R5 where R5 is selected from the group consisting of alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic,
and with the proviso that when R1 is 3,4-dichlorophenyl, R2 is methyl, and R3 is benzyl derived from D-phenylglycine, then X is not xe2x80x94C(O)OCH3,
and still with the further proviso excluding the following known compounds:
when R1 is phenyl, R2 is methyl, X is xe2x80x94C(O)NHxcfx86, then R3 is not methyl, iso-propyl, iso-butyl; and
when R1 is phenyl, R2 is methyl, X is xe2x80x94C(O)NH2, then R3 is not benzyl.
Preferred compounds of formula III above include those set forth below in Table I below:
As above, this invention relates to compounds which inhibit xcex2-amyloid peptide release and/or its synthesis, and, accordingly, have utility in treating Alzheimer""s disease. However, prior to describing this invention in further detail, the following terms will first be defined.
Definitions
The term xe2x80x9cxcex2-amyloid peptidexe2x80x9d refers to a 39-43 amino acid peptide having a molecular weight of about 4.2 kD which peptide is substantially homologous to the form of the protein described by Glenner, et al.1 including mutations and post-translational modifications of the normal xcex2-amyloid peptide. In whatever form, the xcex2-amyloid peptide is approximately a 39-43 amino acid fragment of a large membrane-spanning glycoprotein, referred to as the xcex2-amyloid precursor protein (APP). Its 43-amino acid sequence is:
or a sequence which is substantially homologous thereto.
xe2x80x9cAlkylxe2x80x9d refers to monovalent alkyl groups preferably having from 1 to 10 carbon atoms and more preferably 1 to 6 carbon atoms. This term is exemplified by groups such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, n-hexyl, and the like.
xe2x80x9cSubstituted alkylxe2x80x9d refers to an alkyl group, preferably of from 1 to 10 carbon atoms, having from 1 to 3 substituents selected from the group consisting of alkoxy, substituted alkoxy, acyl, acylamino, acyloxy, amino, aminoacyl, aminoacyloxy, cyano, halogen, hydroxyl, carboxyl, carboxylalkyl, cycloalkyl, oxyacylamino, thiol, thioalkoxy, substituted thioalkoxy, aryl, heteroaryl, heterocyclic, nitro, and mono- and di-alkylamino, mono- and di-(substituted alkyl)amino, mono- and di-cycloalkylamino, mono- and di-arylamino, mono- and di-heteroaryl-amino, mono- and di-heterocyclic amino, and unsymmetric di-substituted aminries having different substituents selected from alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic.
xe2x80x9cAlkylenexe2x80x9d refers to divalent alkylene groups preferably having from 1 to 10 carbon atoms and more preferably 1 to 6 carbon atoms. This term is exemplified by groups such as methylene (xe2x80x94CH2xe2x80x94), ethylene (xe2x80x94CH2CH2xe2x80x94), the propylene isomers (e.g., xe2x80x94CH2CH2CH2xe2x80x94 and xe2x80x94CH(CH3)CH2xe2x80x94) and the like.
xe2x80x9cAlkarylxe2x80x9d refers to -alkylene-aryl groups preferably having from 1 to 10 carbon atoms in the alkylene moiety and from 6 to 10 carbon atoms in the aryl moiety. Such alkaryl groups are exemplified by benzyl, phenethyl and the like.
xe2x80x9cAlkoxyxe2x80x9d refers to the group xe2x80x9calkyl-O-xe2x80x9d. Preferred alkoxy groups include, by way of example, methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, tert-butoxy, sec-butoxy, n-pentoxy, n-hexoxy, 1,2-dimethylbutoxy, and the like.
xe2x80x9cSubstituted alkoxyxe2x80x9d refers to the group xe2x80x9csubstituted alkyl-O-xe2x80x9d where substituted alkyl is as defined above.
xe2x80x9cAlkylalkoxyxe2x80x9d refers to the group xe2x80x9c-alkylene-O-alkylxe2x80x9d where alkylene and alkyl are as defined above. Such groups include, by way of example, methylenemethoxy (xe2x80x94CH2OCH3), ethylenemethoxy (xe2x80x94CH2CH2OCH3), n-propylene-iso-propoxy (xe2x80x94CH2CH2(,H2OCH(CH3)2), methylene-tert-butoxy (xe2x80x94CH2xe2x80x94Oxe2x80x94C(CH3)3) and the like.
xe2x80x9cAlkylthioalkoxyxe2x80x9d refers to the group xe2x80x9c-alkylene-S-alkylxe2x80x9d where alkylene and alkyl are as defined above. Such groups include, by way of example, methylenethiomethoxy (xe2x80x94CH2SCH3), ethylenethiomethoxy (xe2x80x94CH2CH2SCH3), n-propylene-iso-thiopropoxy (xe2x80x94CH2CH2CH2SCH(CH3)2), methylenethio-tert-butoxy (xe2x80x94CH2SC(CH3)3) and the like.
xe2x80x9cAlkenylxe2x80x9d refers to alkenyl groups preferably having from 2 to 10 carbon atoms and more preferably 2 to 6 carbon atoms and having at least 1 and preferably from 1-2 sites of alkenyl unsaturation. Preferred alkenyl groups include ethenyl (xe2x80x94CHxe2x95x90CH2), n-propenyl (xe2x80x94CH2CHxe2x95x90CH2), iso-propenyl (xe2x80x94C(CH3)xe2x95x90CH2), and the like.
xe2x80x9cSubstituted alkenylxe2x80x9d refers to an alkenyl group as defined above having from 1 to 3 substituents selected from the group consisting of alkoxy, substituted alkoxy, acyl, acylamino, acyloxy, amino, aminoacyl, aminoacyloxy, cyano, cycloalkyl, oxyacylamino, halogen, hydroxyl, carboxyl, carboxylalkyl, thiol, thioalkoxy, substituted thioalkzxy, aryl, heteroaryl, heterocyclic, nitro, and mono- and di-alkylamino, mono- and di-(substituted alkyl)amino, mono- and di-cycloalkyl, mono- and di-arylamino, mono- and di-heteroarylamino, mono- and di-heterocyclic amino, and unsymmetric di-substituted amines having different substituents selected from alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic.
xe2x80x9cAlkynylxe2x80x9d refers to alkynyl groups preferably having from 2 to 10 carbon atoms and more preferably 2 to 6 carbon atoms and having at least 1 and preferably from 1-2 sites of alkynyl unsaturation. Preferred alkynyl groups include ethynyl (xe2x80x94Cxe2x89xa1CH), propargyl (xe2x80x94CH2Cxe2x89xa1CH) and the like.
xe2x80x9cSubstituted alkynylxe2x80x9d refers to an alkynyl group as defined above having from 1 to 3 substituents selected from the group consisting of alkoxy, substituted alkoxy, acyl, acylamino, acyloxy, amino, aminoacyl, aminoacyloxy, cyano, cycloalkyl, oxyacylamino, halogen, hydroxyl, carboxyl, carboxylalkyl, thiol, thioalkoxy, substituted thioalkoxy, aryl, heteroaryl, heterocyclic, nitro, and mono- and di-alkylamino, mono- and di-(substituted alkyl)amino, mono- and di-cycloalkylamino, mono- and di-arylamino, mono- and di-heteroarylamino, mono- and di-heterocyclic amino, and unsymmetric di-substituted amines having different substituents selected from alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic.
xe2x80x9cAcylxe2x80x9d refers to the groups alkylxe2x80x94C(O)xe2x80x94, substituted alkylxe2x80x94C(O)xe2x80x94, cycloalkylxe2x80x94C(O)xe2x80x94, arylxe2x80x94C(O)xe2x80x94, heteroarylxe2x80x94C(O)xe2x80x94 and heterocyclicxe2x80x94C(O)xe2x80x94 where alkyl, substituted alkyl, cycloalkyl, arvl, heteroaryl and heterocyclic are as defined herein.
xe2x80x9cAcylaminoxe2x80x9d refers to the group xe2x80x94C(O)NRR where each R is independently hydrogen, alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl. and heterocyclic and where each of alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic are as defined herein.
xe2x80x9cAminoacylxe2x80x9d refers to the group xe2x80x94NRC(O)R where each R is independently hydrogen, alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl, and heterocyclic and where each of alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic are as defined herein.
xe2x80x9cAcyloxyxe2x80x9d refers to the groups xe2x80x94OC(O)-alkyl, xe2x80x94OC(O)-substituted alkyl, xe2x80x94OC(O)-cycloalkyl, xe2x80x94OC(O)-aryl, xe2x80x94C(O)O-heteroaryl-, and xe2x80x94C(O)O-heterocyclic where alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic are as defined herein.
xe2x80x9cAminoacyloxyxe2x80x9d refers to the groups xe2x80x94NRC(O)O-alkyl, xe2x80x94NRC(O)O-substituted alkyl, xe2x80x94NRC(O)O-cycloalkyl, xe2x80x94NRC(O)O-aryl, xe2x80x94NRC(O)O-heteroaryl-, and xe2x80x94NRC(O)O-heterocyclic where R is hydrogen, alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl, and heterocyclic and where each of alkyl, substituted alkyl, cycloalkyl, aryl, he,eroaryl and heterocyclic are as defined herein.
xe2x80x9cOxyacylaminoxe2x80x9d refers to the groups xe2x80x94OC(O)NR-alkyl, xe2x80x94OC(O)NR-substituted alkyl, xe2x80x94OC(O)NR-aryl, xe2x80x94OC(O)NR-heteroaryl-, and xe2x80x94OC(O)NR-heterocyclic where R is hydrogen, alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl, and heterocyclic and where each of alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic are as defined herein.
xe2x80x9cArylxe2x80x9d refers to an unsaturated aromatic carbocyclic group of from 6 to 14 carbon atoms having a single ring (e.g., phenyl) or multiple condensed rings (e.g., naphthyl or anthryl). Preferred aryls include phenyl, naphthyl and the like.
Unless otherwise constrained by the definition for the aryl substituent, such aryl groups can optionally be substituted with from 1 to 3 substituents selected from the group consisting of hydroxy, acyl, acyloxy, alkyl, substituted alkyl, alkoxy, substituted alkoxy, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, amino, aminoacyl, acylamino, aminoacyloxy, oxyacylamino, aryl, aryloxy, carboxyl, carboxylalkyl, cyano, halo, nitro, heteroaryl, trihalomethyl, thioalkoxy, substituted thioalkoxy, mono- and di-alkylamino, mono- and di-(substituted alkyl)amino, mono- and di-cycloalkylamino, mono- and di-arylainino, mono- and di-heteroarylamino, mono- and di-heterocyclic amino, and unsymmetric di-substituted amines having different substituents selected from alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic, and the like. Preferred substituents include alkyl, alkoxy, halo, cyano, nitro, trihalomethyl, and thioalkoxy. When so substituted, such aryl groups are sometimes referred to herein as xe2x80x9csubstituted arylxe2x80x9d.
xe2x80x9cAryloxyxe2x80x9d refers to the group aryl-O- wherein the aryl group is as defined above including optionally SLubstituted aryl groups as also defined above.
xe2x80x9cCarboxyalkylxe2x80x9d refers to the groups xe2x80x94C(O)O-alkyl and xe2x80x94C(O)O-substituted alkyl where alkyl and substituted alkyl are as defined herein.
xe2x80x9cCycloalkylxe2x80x9d refers to cyclic alkyl groups of from 3 to 20 carbon atoms having a single cyclic ring or multiple condensed rings (including aromatic rings fused to the cycloalkyl ring) which can be optionally substituted with from 1 to 3 alkyl groups. Such cycloalkyl groups include, by way of example, single ring structures such as cyclopropyl, cyclobutyl, cyclopentyl, cyclooctyl, 1-methylcyclopropyl, 2-methylcyclopentyl, 2-methylcyclooctyl, and the like, or multiple ring structures such as dibenzosuberane, adamantanyl, and the like.
xe2x80x9cCycloalkenylxe2x80x9d refers to cyclic alkenyl groups of from 4 to 8 carbon atoms having a single cyclic ring or multiple condensed rings and at least one point of internal unsaturation which can be optionally substituted with from 1 to 3 alkyl groups. Examples of suitable cycloalkenyl groups include, for instance, cyclobut-2-enyl, cyclopent-3-enyl, cyclooct-3-enyl and the like.
xe2x80x9cHaloxe2x80x9d or xe2x80x9chalogenxe2x80x9d refers to fluoro, chloro, bromo and iodo and preferably is either chloro or bromo.
xe2x80x9cHeteroarylxe2x80x9d refers to a monovalent aromatic group of from 2 to 10 carbon atoms and 1 to 4 heteroatoms selected from oxygen, nitrogen and sulfur within the ring.
Unless otherwise constrained by the definition for the heteroaryl substituent, such heteroaryl groups can be optionally substituted with 1 to 3 substituents selected from the group consisting of hydroxy, acyl, acyloxy, alkyl, substituted alkyl, alkoxy, substituted alkoxy, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, amino, aminoacyl, acylamino, aminoacyloxy, oxyacylamino, aryl, aryloxy, carboxyl, carboxylalkyl, cyano, halo, nitro, heteroaryl, trihalomethyl, thioalkoxy., substituted thioalkoxy, mono- and di-alkylamino, mono- and di-(substituted alkyl)amino, mono- and di-cycloalkylamino, mono- and di-arylamino, mono-and di-heteroarilamino, mono- and di-heterocyclic amino, and unsymmetric di-substituted amines having different substituents selected from alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic, and the like. Such heteroaryl groups can have a single ring (e.g., pyridyl, furyl, etc.) or multiple condensed rings (e.g., indolizinyl or benzothienyl). Preferred heteroaryls include pyridyl, pyrrolyl, and furyl. When so substituted, such heteroaryl groups are sometimes referred to herein as xe2x80x9csubstituted heteroarylxe2x80x9d.
xe2x80x9cHeterocyclexe2x80x9d or xe2x80x9cheterocyclicxe2x80x9d refers to a monovalent saturated or unsaturated group having a single ring, or multiple condensed rings, from 1 to 12 carbon atoms and from 1 to 4 hetero atoms selected from nitrogen, sulfur or oxygen within the ring.
Unless otherwise constrained by the definition for the heterocyclic substituent, such heterocyclic groups can be optionally substituted with 1 to 3 substituents selected from the group consisting of hydroxy, acyl, acyloxy, alkyl, substituted alkyl, alkoxy, substituted alkoxy, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, amino, aminoacyl, acylamino, aminoacyloxy, oxyacylamino, aryl, aryloxy, carboxyl, carboxylalkyl, cyano, halo, nitro, heteroaryl, trihalomethyl, thioalkoxy, substituted thioalkoxy, mono- and di-alkylamino, mono- and di-(substituted alkyl)amino, mono- and di-arylamino, mono-and di-heteroarylamino, mono- and di-heterocyclic amino, and unsymmetric di-substituted amines having different substituents selected from alkyl, substituted alkyl, cycloalkyl, aryl, heteroaryl and heterocyclic, and the like. Such heterocyclic groups can have a single ring or multiple condensed rings. Preferred heterocyclics include morpholino, piperidinyl, and the like.
Examples of heterocycles and heteroaryls include, but are not limited to, furan, thiophene, thiazole, oxazole, pyrrole, imidazole, pyrazole, pyridine, pyrazine, pyrimidine, pyridazine, indolizine, isoindole, indole, indazole, purine, quinolizine, isoquinoline, quinoline, phthalazine, naphthylpyridine, quinoxaline, quinazoline, cinnoline, pteridine, carbazole, carboline, phenanthridine, acridine, phenanthroline, isothiazole, phenazine, isoxazole, phenoxazine, phenothiazine, imidazolidine, imidazoline, piperidine, piperazine, indoline, phthalimide, 1,2,3,4-tetrahydroisoquinoline, 4,5,6,7-tetrahydrobenzo[b]thiophene, thiazole, thiazolidine, thiophene, benzo[b]thiophene, morpholino, piperidinyl, pyrrolidine, tetrahydrofuranyl, and the like.
xe2x80x9cThiolxe2x80x9d refers to the group xe2x80x94SH.
xe2x80x9cThioalkoxyxe2x80x9d refers to the group xe2x80x94S-alkyl.
xe2x80x9cSubstituted thioalkoxyxe2x80x9d refers to the group xe2x80x94S-substituted alkyl.
xe2x80x9cThioaryloxyxe2x80x9d refers to the group aryl-Sxe2x80x94 wherein the aryl group is as defined above including optionally substituted aryl groups as also defined above.
xe2x80x9cThioheteroaryloxyxe2x80x9d refers to the group heteroaryl-Sxe2x80x94 wherein the heteroaryl group is as defined above including optionally substituted aryl groups as also defined above.
In the compounds of formula I, Rb and Rc can be fused to form a heteroaryl or heterocyclic ring with the phenyl ring. Fusion in this manner results in a fused bicyclic ring structure of the formula: 
where Rxe2x80x2 is as defined above and A is the fused heteroaryl or heterocyclic group as these terms are as defined above wherein the two atoms of the phenyl ring are included in the total atoms present in the heteroaryl or heterocyclic group. Examples of such fused ring systems include, for instance, indol-5-yl, indol-6-yl, thionaphthen-5-yl, thionaphthen-6-yl, isothionaphthen-5-yl, isothionaphthen-6-yl, indoxazin-5-yl, indoxazin-6-yl, benzoxazol-5-yl, benzoxazol-6-yl, anthranil-5-yl, anthiranil-6-yl, quinolin-6-yl, quinolin-7-yl, isoquinolin-6-yl, isoquinolin-7-yl, cinnolin-6yl, cinnolin-7-yl, quinazolin-6yl, quinazolin-7-yl, benzofuran-5-yl, benzofuran-6-yl, isobenzofuran-5-yl, isobenzofuran-6-yl, and the like.
xe2x80x9cPharmaceutically acceptable saltxe2x80x9d refers to pharmaceutically acceptable salts of a compound of Formula I which salts are derived from a variety of organic and inorganic counter ions well known in the art and include, by way of example only, sodium, potassium, calcium, magnesium, ammonium, tetraalkylammonium, and the like; and when the molecule contains a basic functionality, salts of organic or inorganic acids, such as hydrochloride, hydrobromide, tartrate, mesylate, acetate, maleate, oxalate and the like.
Compound Preparation
The compounds of formula I above are readily prepared via several divergent synthetic routes with the particular route selected relative to the ease of compound preparation, the commercial availability of starting materials, and the like.
In one synthetic method, the R1 group of the amino acid NH2CH(R2)COOH or an ester thereof is first introduced onto the molecule. Afterwards, conventional coupling of the first R1NHCH(R2)COOH or ester thereof with the amine of NH2CH(R3)C(O)Y provides for compounds of formula I wherein X is xe2x80x94C(O)Y.
Similarly, conventional reduction of the xe2x80x94C(O)Y group leads to xe2x80x94CH2OH groups and the like.
The introduction of the R1 group onto the amino acid NH2CH(R2)COOH or ester thereof can be accomplished using several methods. For example, conventional coupling of a halo acetic acid with a primary amine forms an amino acid as shown in reaction (1) below: 
wherein R1 and R2 are as defined above and Xxe2x80x2 is preferably a halo group such as chloro or bromo. Alternatively, leaving groups other than halo may be employed such as triflate, mesylate, tosylate and the like. Additionally, suitable esters of 1 may be employed in this reaction.
Reaction (1) involves coupling of a suitable haloacetic acid derivative 1 with a primary aryl/heteroarylamine 2 under conditions which provide for amino acid 3. This reaction is described by, for example, Yates, et al.10 and proceeds by combining approximately stoichiometric equivalents of haloacetic acid 1 with primary aryl/heteroarylamine 2 in a suitable inert diluent such as water, dimethylsulfoxide (DMSO) and the like. The reaction employs an excess of a suitable base such as sodium bicarbonate, sodium hydroxide, etc. to scavenge the acid generated by the reaction. The reaction is preferably conducted at from about 25xc2x0 C. to about 100xc2x0 C. until reaction completion which typically occurs within 1 to about 24 hours. This reaction is further described in U.S. Pat. No. 3,598,859, which is incorporated herein by reference in its entirety. Upon reaction completion, N-aryl/N-heteroaryl amino acid 3 is recovered by conventional methods including precipitation, chromatography, filtration and the like.
In reaction (1), each of the reagents (haloacetic acid 1, primary aryl/heteroarylamine 2 and alcohol 3 are well known in the art with a plurality of each being commercially available.
In an alternative embodiment, the R1 group can be coupled to an alanine ester (or other suitable amino acid ester) by conventional N-arylation. For example, a stoichiometric equivalent or slight excess of the amino acid ester can be dissolved in a suitable diluent such as DMSO and coupled with a haloaryl compound, X-R1 where X is a halo group such as fluoro, chloro or bromo and R1 is as defined above. The reaction is conducted in the presence of an excess of base such as sodium hydroxide to scavenge the acid generated by the reaction. The reaction typically proceeds at from 15xc2x0 C. to about 250xc2x0 C. and is complete in about 1 to 24 hours. Upon reaction completion, N-aryl amino acid ester is recovered by conventional methods including chromatography, filtration and the like.
In still another alternative embodiment, the esterified amino acids of formula I above can be prepared by reductive amination of a suitable 2-oxocarboxylic acid ester (such as a pyruvate ester) in the manner illustrated in Reaction (2) below: 
wherein R1 and R2 are as defined above.
In reaction (2), approximately stoichiometric equivalents of a 2-oxocarboxylic acid ester 6 and arylainine 2 are combined in an inert diluent such as methanol, ethanol and the lilce and the reaction solution treated under conditions which provide for imine formation (not shown). The imine formed is then reduced under conventional conditions by a suitable reducing agent such as sodium cyanoborohydride, H2/palladium on carbon and the like to form the N-aryl amino acid ester 5. In a particularly preferred embodiment, the reducing agent is H2/palladium on carbon which is incorporated into the initial reaction medium which permits irvirte reduction in situ in a one pot procedure to provide for the N-aryl amino acid ester 5.
The reaction is preferably conducted at from about 20xc2x0 C. to about 80xc2x0 C. at a pressure of from 1 to 10 atmospheres until reaction completion which typically occurs within 1 to about 24 hours. Upon reaction completion, N-aryl amino acid ester 5 is recovered by conventional methods including chromatography, filtration and the like.
Subsequent hydrolysis of the ester 5 leads to the corresponding carboxylic acid derivative.
A further embodiment for preparing N-aryl amino acids includes aromatic nucleophilic substitution of fluorobenzenes by the amine group of an amino acid.
The carboxylic acid derivative 5 is then coupled under conventional conditions well known in the art with a compound of the formula NH2CH(R3)C(O)Y where R3 and Y are as defined above. Such coupling leads to compounds of formula I. Subsequent modifications (e.g., reduction) lead to further compounds of formula I.
When Y is an ester group, conventional transesterification techniques can be used to prepare a variety of different ester groups on the compounds of formula I. Numerous techniques are known in the art to effect transesterification and each technique merely replaces the ester group with a different ester group derived from the corresponding alcohol or thioalcohol and, in some cases, a catalyst such as titanium (IV) iso-propoxide is used to facilitate reaction completion. In one technique, the alcohol or thioalcohol is first treated with sodium hydride in a suitable diluent such as toluene to form the corresponding sodium alkoxide or thioalkoxide which is then employed to effect transesterification. The efficierncy of this technique makes it particularly useful with high boiling and/or expensive alcohols.
In another transesterification technique, the ester to be transesterified is placed in a large excess of the alcohol or thioalcohol which effects transesterification. A catalytic amount of sodium hydride is then added and the reaction proceeds quickly under conventional conditions to provide the desired transesterified product. Because this protocol requires the use of a large excess of alcohol or thioalcohol, this procedure is particularly useful when the alcohol is inexpensive.
Transesterification provides a lacile means to provide for a multiplicity of different ester substituents on the compounds of formula I above. In all cases, the alcohols and thioalcohols employed to effect transesterification are well known in the art with a significant number being commercially available.
Other methods for preparing the esters of this invention include, by way of example, first hydrolyzing the ester to the free acid followed by O-alkylation with, e.g., a haloalkyl group in the presence of a base such as potassium carbonate.
Still other methods for the preparation of compounds of formula I are provided in the examples below.
Compounds where X is xe2x80x94CR4R4Yxe2x80x2 are readily prepared by coupling, e.g., an amino alcohol H2NCHR3CR4R4OH, to the carboxyl group of R1NHCHR2C(O)OH under standard coupling conditions well known in peptide coupling chemistry which can use well known coupling reagents such as S carbodiimides with or without the use of well known additives such as N-hydroxysuccinimide, 1-hydroxybenzotriazole, etc. If necessary, well known blocking groups on Yxe2x80x2 can be employred to protect the group during coupling. Such blocking groups are particularly desirable when Yxe2x80x2 is an amino group.
The reaction is conventionally conducted in an inert aprotic diluent such as dimethylformamide, dichloromethane, chloroform, acetonitrile, tetrahydrofuran and the like. Upon reaction completion, any blocking groups on Yxe2x80x2 are selectively removed to provide for the desired compound.
When Yxe2x80x2 is xe2x80x94OH or xe2x80x94SH, post-synthetic conversion of these groups to the corresponding esters (i.e., xe2x80x94OC(O)R5), disulfides (i.e., xe2x80x94SSR5) and xe2x80x94SSC(O)R5 groups is accomplished using well known chemistry. For example, ester synthesis requires only reaction with a suitable acid such as acetic acid (R7=methyl), acid halide (e.g., acid chloride) or acid anhydride under suitable esterification conditions.
When one of R4 groups is hydrogen, post-synthetic oxidation of the xe2x80x94CHR4OH group leads to the ketone derivatives. Alternatively, such ketones can be prepared by coupling the suitable aminoketone HCl salt with the terminal carboxyl group of the amino acid.
In these synthetic methods, the starting materials can contain a chiral center (e.g., alanine) and, when a racemic starting material is employed, the resulting product is a mixture of diastereomers or R,S enantiomers. Alternatively, a chiral isomer of the starting material can be employed and, if the reaction protocol employed does not racemize this starting material, a chiral product is obtained. Such reaction protocols can involve inversion of the chiral center during synthesis.
Accordingly, unless otherwise indicated, the products of this invention are a mixture of diastereomers (if two or more chiral centers are present) or R,S enantiomers (if only one chiral center is present). Preferably, however, when a chiral product is desired, the chiral product corresponds to the L-amino acid derivative. Alternatively, chiral products can be obtained via purification techniques which separates diastereomers or enantiomers from a R,S mixture to provide for one or the other stereoisomer. Such techniques are well known in the art.
Pharmaceutical Formulations
When employed as pharmaceuticals, the compounds of formula I are usually administered in the form of pharmaceutical compositions. These compounds can be administered by a variety of routes including oral, rectal, transdermal, subcutaneous, intravenous, intramuscular, and intranasal. These compounds are effective as both injectable and oral compositions. Such compositions are prepared in a manner well known in the pharmaceutical art and comprise at least one active compound.
This invention also includes pharmaceutical compositions which contain, as the active ingredient, one or more of the compounds of formula I above associated with pharmaceutically acceptable carriers. In making the compositions of this invention, the active ingredient is usually mixed with an excipient, diluted by an excipient or enclosed within such a carrier which can be in the form of a capsule, sachet, paper or other container. When the excipient serves as a diluent, it can be a solid, semi-solid, or liquid material, which acts as a vehicle, carrier or medium for the active ingredient. Thus, the compositions can be in the form of tablets, pills, powders, lozenges, sachets, cachets, elixirs, suspensions, emulsions, solutions, syrups, aerosols (as a solid or in a liquid medium), ointments containing, for example, up to 10% by weight of the active compound, soft and hard gelatin capsules, suppositories, sterile injectable solutions, and sterile packaged powders.
In preparing a formulation, it may be necessary to mill the active compound to provide the appropriate particle size prior to combining with the other ingredients. If the active compound is substantially insoluble, it ordinarily is milled to a particle size of less than 200 mesh. If the active compound is substantially water soluble, the particle size is normally adjusted by milling to provide a substantially uniform distribution in the formulation, e.g. about 40 mesh.
Some examples of suitable excipients include lactose, dextrose, sucrose, sorbitol, mannitol, starches, gum acacia, calcium phosphate, alginates, tragacanth, gelatin, calcium silicate, microcrystalline cellulose, polyvinylpyrrolidone, cellulose, sterile water, syrup, and methyl cellulose. The formulations can additionally include: lubricating agents such as talc, magnesium stearate, and mineral oil; wetting agents; emulsifying and suspending agents; preserving agents such as methyl- and propylhydroxybenzoates; sweetening agents; and flavoring agents. The compositions of the invention can be formulated so as to provide quick, sustained or delayed release of the active ingredient after administration to the patient by employing procedures known in the art.
The compositions are preferably formulated in a unit dosage form, each dosage containing from about 5 to about 100 mg, more usually about 10 to about 30 mg, of the active ingredient. The term xe2x80x9cunit dosage formsxe2x80x9d refers to physically discrete units suitable as unitary dosages for human subjects and other mammals, each unit containing a predetermined quantity of active material calculated to produce the desired therapeutic effect, in association with a suitable pharmaceutical excipient. Preferably, the compound of formula I above is employed at no more than about 20 weight percent of the pharmaceutical composition, more preferably no more than about 15 weight percent, with the balance being pharmaceutically inert carrier(s).
The active compound is effective over a wide dosage range and is generally administered in a pharmaceutically effective amount. It, will be understood, however, that the amount of the compound actually administered will be determined by a physician, in the light of the relevant circumstances, including the condition to be treated, the chosen route of administration, the actual compound administered, the age, weight, and response of the individual patient, the severity of the patient""s symptoms, and the like.
For preparing solid compositions such as tablets, the principal active ingredient is mixed with a pharmaceutical excipient to form a solid preformulation composition containing a homogeneous mixture of a compound of the present invention. When referring to these preformulation compositions as homogeneous, it is meant that the active ingredient is dispersed evenly throughout the composition so that the composition may be readily subdivided into equally effective unit dosage forms such as tablets, pills and capsules. This solid preformulation is then subdivided into unit dosage forms of the type described above containing from, for example, 0.1 to about 500 mg of the active ingredient of the present invention.
The tablets or pills of the present invention may be coated or otherwise compounded to provide a dosage form affording the advantage of prolonged action. For example, the tablet or pill can comprise an inner dosage and an outer dosage component, the latter being in the form of an envelope over the former. The two components can be separated by an enteric layer which serves to resist disintegration in the stomach and permit the inner component to pass intact into the duodenum or to be delayed in release. A variety of materials can be used for such enteric layers or coatings, such materials including a number of polymeric acids and mixtures of polymeric acids with such materials as shellac, cetyl alcohol, and cellulose acetate.
The liquid forms in which the novel compositions of the present invention may be incorporated for administration orally or by injection include aqueous solutions, suitably flavored syrups, aqueous or oil suspensions, and flavored emulsions with edible oils such as corn oil, cottonseed oil, sesame oil, coconut oil, or peanut oil, as well as elixirs and similar pharmaceutical vehicles.
Compositions for inhalation or insufflation include solutions and suspensions in pharmaceutically acceptable, aqueous or organic solvents, or mixtures thereof, and powders. The liquid or solid compositions may contain suitable pharmaceutically acceptable excipients as described supra. Preferably the compositions are administered by the oral or nasal respiratory route for local or systemic effect. Compositions in preferably pharmaceutically acceptable solvents may be nebulized by use of inert gases. Nebulized solutions may be inhaled directly from the nebulizing device or the nebulizing device may be attached to a face mask tent, or intermittent positive pressure breathing machine. Solution, suspension, or powder compositions may be administered, preferably orally or nasally, from devices which deliver the formulation in an appropriate manner.